As a GC analysis technique, a technique called a comprehensive two-dimensional GC (also called “GC×GC”) is known (refer to Patent Literature 1). The comprehensive two-dimensional GC first separates various components in a sample in a first-dimension column (hereinafter, called a “primary column”), and introduces the eluted components into a modulator. The modulator repeats an operation of trapping the introduced components at constant time intervals (typically, about several seconds to several tens of seconds; the time interval is usually called “modulation time”) and subsequently drawing the components in a significantly narrow time band, and introducing the components into a second-dimension column (hereinafter, called a “secondary column”). Typically, in the primary column, components are separated under a separation condition that allows elution similar to that of a typical GC or elution slightly slower than that of a typical GC. On the other hand, as a secondary column, a column that has a different polarity and a smaller inner diameter in comparison with the primary column is adopted. Components are separated under a condition that allows elution to be completed in a predetermined modulation time.
Accordingly, in the comprehensive two-dimensional GC, the secondary column can be used to separate multiple compounds that have not been separated in the primary column and have peaks overlap with each other, thereby allowing the separation performance to be significantly improved in comparison with a typical GC. Therefore, this GC is significantly effective in analyzing a sample that contains many compounds having close retention times, typically in analyzing hydrocarbons in diesel fuel and the like.
Unlike a multi-dimensional GC that adopts multiple detectors corresponding to respective columns, the comprehensive two-dimensional GC obtains a detection signal through a single detector connected at an output port of a secondary column. Accordingly, though components are separated in columns in two stages, data output from the detector is one series of chronological order data items. Therefore, by plotting the thus obtained data items in the occurrence order, a chromatogram similar to that of a typical GC, i.e., a chromatogram where the abscissa indicates the temporal axis and the ordinate indicates the signal strength axis, can be created. FIG. 2A indicates an example of a one-dimensional chromatogram created in this way.
As described above, in many cases, the comprehensive two-dimensional GC includes two columns having different separation characteristics. Accordingly, in order to represent the state of separation in each column in a manner easy to understand, a two-dimensional chromatogram is created where the retention time in the primary column and the retention time in the secondary column are represented in respective two axes orthogonal to each other and the signal strength is represented as contour lines, or a three-dimensional chromatogram is created where the signal strength is represented as the third axis. As data processing software dedicated to a comprehensive two-dimensional GC for creating such a multi-dimensional chromatogram, “GC Image” (refer to Non Patent Literature 1) provided by GC Image LLC in the U.S. is well known.
FIG. 2B is an explanatory diagram of data arrangement which results when a two-dimensional chromatogram is created from the one-dimensional chromatogram data as shown in FIG. 2A. The range of the ordinate of this graph indicates the modulation time. An operation is repeated that sequentially plots the one-dimensional chromatogram data along the ordinate from the bottom (0) in the upward direction (solid arrows in the diagram), and, upon reaching the modulation time, moves along the abscissa in the right direction while returning to the bottom of the ordinate (broken lines in the diagram), and plots the data again in the upward direction along the ordinate. This repetition can create, for example, a two-dimensional chromatogram (two-dimensional contour line chromatogram) as shown in FIG. 2C.
In a temperature rising analysis, the abscissa indicates the order of boiling points, and the ordinate indicates the polarity order. Accordingly, this two-dimensional chromatogram can facilitate understanding of the characteristics of each compound, and identifying contained compounds even when many types of compounds are contained.
Typically, in the comprehensive two-dimensional GC, data obtained from sample analysis is temporarily stored in a storage device, such as a hard disk. Subsequently, the data is read from the storage device at an appropriate timing, and processed by the dedicated data processing software as described above. The processes of collecting data from the comprehensive two-dimensional GC and storing the collected data in the storage device are performed using software for a typical GC or GC/MS instead of the comprehensive two-dimensional GC. However, the typical GC does not originally have a concept of “modulation time”. Accordingly, the collected chromatogram data does not contain data (parameter information) that indicates the modulation time as one of analysis conditions. Thus, conventionally, an analyst records modulation time information during execution of analysis. When the chromatogram data is read by the data processing software dedicated to the comprehensive two-dimensional GC, the analyst inputs the modulation time as one of processing parameters (refer to Non Patent Literature 2). Such operations are complicated for the analyst, and cause a possibility that input errors and the like generate incorrect results.
The comprehensive two-dimensional LC that executes analysis similar to that of the comprehensive two-dimensional GC is also in situations similar to the above situations.